Definition and Usage
The substring() method extracts the characters from a string, between two specified indices, and returns the new sub string.
This method extracts the characters in a string between "start" and "end", not including "end" itself.
If "start" is greater than "end", this method will swap the two arguments, meaning str.substring(1,4) == str.substring(4,1).
If either "start" or "stop" is less than 0, it is treated as if it were 0.
Note: The substring() method does not change the original string.
Extract characters from a string:
var str = "Hello world";
var res = str.substring(1,4);
The result of res will be: